Existing technology for providing a glass coating on a glass stream involve the introduction of multiple glass streams in the forehearth or furnace section of the glass forming operation. This requires new equipment to be installed for the handling of main glass stream as well as the coating glasses.
Typical patents showing such construction, for example, are U.S. Pat. Nos. 1,828,217, 3,291,584, 3,554,726, 3,960,530, 4,023,953, 4,217,123, 4,299,609, 4,381,932, 4,740,401 and 5,204,120.
Another problem with respect to the making of coated glass streams is that relating to orifice rings through which the coated glass passes. In conventional orifice rings, the ceramic orifice ring is held in a metal pan and isolated from the pan by a layer of insulation powder. The orifice ring may be either electrically or gas fired. Gas fired versions have had limited use due to the difficulty in transferring the heat of combustion into the confined area of the orifice ring.
Among the objectives of the invention are to provide a method and apparatus for delivering a coated glass stream for forming charges of glass; wherein the introduction of glass streams is maintained external to the melting, conditioning and delivery systems of the glass manufacturing process; which may be retrofitted to existing installations; and which includes an orifice ring assembly that permits the glass stream to be coated uniformly with a second glass stream.
Among the further objectives of the present invention are to provide a gas-fired orifice ring which supplies controlled high intensity heating to the outer surface of the ring thereby compensating for external heat loss; which yields higher temperatures in the area surrounding the orifice ring and which utilizes ordinary gas-air mixtures.
In accordance with the invention the method comprises delivering a glass stream having a first inner layer and a second outer layer comprising providing a vertical orifice, delivering molten glass from a first source through the orifice, providing a gap about the orifice intermediate its upper and lower ends, delivering glass from a second source about the gap such that the glass from the second source flows through the gap to provide an outer layer about the glass from said first source as it flows through the orifice, and controlling the size and shape of the gap parallel to the flow and the size of the gap perpendicular to the flow such that the gap provides sufficient flow resistance and the gap is of sufficient size and shape to prevent clogging. The method includes the step of providing passages for the flow of the glass from the second source and controlling the size and shape of the passages such that the passages are sufficiently large to minimize flow resistance therein and to provide sufficient pressure to force the glass through the gap and provide less resistance than the metering gap. The method also includes providing a plurality of orifices, each having a gap, delivering glass from the first source through each of the orifices, delivering glass from the second source to the gaps and controlling the size and shapes of such gaps.
The apparatus comprises means for delivering a glass stream having a first inner layer and a second outer layer, means for providing a vertical orifice, means for delivering molten glass from a first source through said orifice, means for providing a gap about said orifice intermediate its upper and lower ends, means for delivering glass from a second source about said gap such that the glass from said second source flows through said gap to provide an outer layer about said glass from said first source as it flows through said orifice, and means for controlling the size and shape of the gap parallel to the flow and the size of the gap perpendicular to the flow such that the gap provides sufficient flow resistance and the gap is of sufficient size and shape to prevent clogging. The apparatus further includes means for providing passages for the flow of the glass from the second source and controlling the size and shape of said passages being such that the passages are sufficiently large to minimize flow resistance therein and to provide sufficient pressure to force the glass through the gap and provide less resistance than said metering gap. The apparatus also includes means for providing a plurality of orifices, each having a gap, means for delivering glass from said first source through each of said orifices, means for delivering glass from said second source to said gaps and means for controlling the size and shapes of such gaps. Specifically, the apparatus comprises an orifice ring assembly which allows one or more glass streams to be coated uniformly with a second glass. The device is constructed in such a way that it (a) delivers the required main stream glass to the glass forming operation, (b) creates a suitable flow resistance to the second glass such that coating is of the proper thickness and uniform, and (c) does not allow glass-refractory particles to become entrained in the system.
In accordance with another aspect of the invention there is provided a gas fired orifice ring that forms a combustion chamber adjacent the underside of the orifice ring such that high temperatures with the combustion ring heat both the periphery and the inner areas surrounding the orifice through which the coated glass stream passes.